Support creating FileDescriptors dynamically from binary data.

Related to #658 and #5007.

1 files changed, 9 insertions, 3 deletions

diff --git a/csharp/src/Google.Protobuf/Reflection/FieldDescriptor.cs b/csharp/src/Google.Protobuf/Reflection/FieldDescriptor.cs
index 2a3d5c7a..152467d8 100644
--- a/csharp/src/Google.Protobuf/Reflection/FieldDescriptor.cs
+++ b/csharp/src/Google.Protobuf/Reflection/FieldDescriptor.cs
@@ -116,13 +116,18 @@ namespace Google.Protobuf.Reflection
         /// that is the responsibility of the accessor.
         /// </para>
         /// <para>
-        /// The value returned by this property will be non-null for all regular fields. However,
-        /// if a message containing a map field is introspected, the list of nested messages will include
+        /// In descriptors for generated code, the value returned by this property will be non-null for all
+        /// regular fields. However, if a message containing a map field is introspected, the list of nested messages will include
         /// an auto-generated nested key/value pair message for the field. This is not represented in any
         /// generated type, and the value of the map field itself is represented by a dictionary in the
         /// reflection API. There are never instances of those "hidden" messages, so no accessor is provided
         /// and this property will return null.
         /// </para>
+        /// <para>
+        /// In dynamically loaded descriptors, the value returned by this property will current be null;
+        /// if and when dynamic messages are supported, it will return a suitable accessor to work with
+        /// them.
+        /// </para>
         /// </remarks>
         public IFieldAccessor Accessor => accessor;
         
@@ -330,7 +335,8 @@ namespace Google.Protobuf.Reflection
         private IFieldAccessor CreateAccessor()
         {
             // If we're given no property name, that's because we really don't want an accessor.
-            // (At the moment, that means it's a map entry message...)
+            // This could be because it's a map message, or it could be that we're loading a FileDescriptor dynamically.
+            // TODO: Support dynamic messages.
             if (propertyName == null)
             {
                 return null;